Genetic mapping and legume synteny of aphid resistance in African cowpea (Vigna unguiculata L. Walp.) grown in California

Abstract

The cowpea aphid Aphis craccivora Koch (CPA) is a destructive insect pest of cowpea, a staple legume crop in Sub-Saharan Africa and other semiarid warm tropics and subtropics. In California, CPA causes damage on all local cultivars from early vegetative to pod development growth stages. Sources of CPA resistance are available in African cowpea germplasm. However, their utilization in breeding is limited by the lack of information on inheritance, genomic location and marker linkage associations of the resistance determinants. In the research reported here, a recombinant inbred line (RIL) population derived from a cross between a susceptible California blackeye cultivar (CB27) and a resistant African breeding line (IT97K-556-6) was genotyped with 1,536 SNP markers. The RILs and parents were phenotyped for CPA resistance using field-based screenings during two main crop seasons in a ‘hotspot’ location for this pest within the primary growing region of the Central Valley of California. One minor and one major quantitative trait locus (QTL) were consistently mapped on linkage groups 1 and 7, respectively, both with favorable alleles contributed from IT97K-556-6. The major QTL appeared dominant based on a validation test in a related F2 population. SNP markers flanking each QTL were positioned in physical contigs carrying genes involved in plant defense based on synteny with related legumes. These markers could be used to introgress resistance alleles from IT97K-556-6 into susceptible local blackeye varieties by backcrossing.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-015-0254-0) contains supplementary material, which is available to authorized users.

A novel aphid resistance locus in cowpea identified by combining SSR and SNP markers

“…QTL mapping using phenotypic data from Huynh et al. () confirmed that CP 171F/172R was not associated with the two aphid resistance QTLs identified on LG 1 (Vu05) and LG 7 (Vu02) in the African cowpea genotype IT97K‐556‐6, which confer resistance to cowpea aphid populations in California.…”

“…Individual plant number 148, which expressed resistance to aphid, had recovered 95% of the ‘Zaayura’ background. Based on marker profiles of 81 BC 4 F 1 individuals, there was no significant linkage between CP 171F/172R and any of the 137 SNPs, including the SNP markers 1_0906 and 1_0755 that flank a major QTL region for aphid resistance on LG 7 (Vu02) in a different mapping population (Huynh et al., ).…”

“…The physical distances of the LG 10 SNP markers also are indicated on Figure 2. LG 10 corresponds to Vu10 in the new cowpea pseudomolecules designation (Lonardi et al, 2017; see https://phytozome.jgi.doe.gov/pz/portal.html#!info?alias= Org_Vunguiculata_er). QTL mapping using phenotypic data from Huynh et al (2015) confirmed that CP 171F/172R was not associated with the two aphid resistance QTLs identified on LG 1 (Vu05) and LG 7 (Vu02) in the African cowpea genotype IT97K-556-6, which confer resistance to cowpea aphid populations in California.…”

Perspectives on the Application of Next-generation Sequencing to the Improvement of Africa’s Staple Food Crops

“…These approaches are being adopted in crops of importance in developing countries such as in maize and wheat [121], rice [124], pulses (legumes) [11], cassava [118,120], cowpea [125], lentil [126], soybean [127,128], and pigeon pea [129]. With respect to the best practice for GS, various models are being put forward [113].…”

Screening of cowpea (Vigna unguiculata (L.) Walp.) lines for resistance to three Aphids (Aphis craccivora Koch) strains in Burkina Faso

“…So, new resistant sources need to be developed and deployed in cowpea growing areas where aphids occur in order to reduce the risk of resistance break-down. Genetic studies on aphid resistance have also been done (Bata et al, 1987;Pathak and Krishna, 1991;Huynh et al, 2015) but the results of these studies differ from one to another raised questions about the mode of inheritance to aphids. Thus, to increase the understanding of aphid resistance, it is necessary to find out more sources of resistance.…”